Removal of antibiotics and antibiotic resistance genes from urban rivers using a photocatalytic-and-bionic artificial ecosystem

Abstract

The behavior and removal of 4 antibiotics (azithromycin, sulfamethoxazole, ciprofloxacin and tetracycline) and 8 typical corresponding antibiotic resistance genes (ARGs) including sul1, sul2, tetX, tetM, qnrS, qnrD, ermB and 16S rDNA in urban rivers were investigated using a developed photocatalytic-and-bionic artificial ecosystem (PCBS). According to the hybrid combinations of AquaMats eco-based bionic grass and 2 photocatalysts, the system was constructed with 4 configurations, A-the control, i.e., no bionic grass or photocatalyst, B-only bionic grass, C-bionic grass loaded with graphitic carbon nitride (g-C3N4), and D-bionic grass loaded with TiO2, operated in a medium-scale running cyclical flume simulating an urban river. The results demonstrated that the optimal unit load of 2 photocatalysts on the bionic grass was 8.25 g/m2. The overall removal rates of the antibiotics ranged from 21.2% to 64.4%, while those for the ARGs varied from 0.7% to 28.1% in the sediment and 1.0%–65.9% in the aqueous phase by the PCBS. After comprehensive consideration of the removal effects of target contaminants, the system of configuration C could be the best choice. Furthermore, microbial structure analysis showed Proteobacteria were the most dominant bacterial species in the microbial communities in the aqueous phase and the sediment, indicating that microbial degradation was also responsible for the fate of antibiotics in the PCBS. The findings from this study suggested the applicability of PCBS for the removal of antibiotics and ARGs from urban rivers and provided new insights about the combination of bionic grass and photocatalysts within the system, which could be crucial in the removal. PCBS developed with bionic grass loaded with photocatalysts in the future could be a promising technology for the removal of emerging contaminants from urban rivers.